如何用python写一个循环，或者其他方式，完成批量选取内容并保存。

Question

下面是将文件 split__1.fasta中选取一段序列，如下421至480. 存于selected_split_1.fasta文件中__。
如何写一个循环，可以从split__1.fasta 至 split__68.fasta，中分别选取421至480. 并存于selected_split_1.fasta至selected_split_68.fasta文件中文件中

from Bio import SeqIO

fin = open('split_1.fasta', 'r')
fout = open('selected_split_1.fasta', 'w')

with open("selected_split_1.fasta","w") as f:
        for seq_record in SeqIO.parse("split_1.fasta", "fasta"):
                f.write(">")
                f.write(str(seq_record.id) + "\n")
                f.write(str(seq_record.seq[421:480]) + "\n")  #start 421 to end 480 base positions

fin.close()
fout.close()

Answer 1

from Bio import SeqIO

for xx in range(1, 68):
xn = "split__" + str(xx) + ".fasta"
yn = "selected_split_" + str(xx) + ".fasta"

fin = open(xn, 'r')
fout = open(yn, 'w')

with open(yn,"w") as f:
for seq_record in SeqIO.parse(xn, "fasta"):
f.write(">")
f.write(str(seq_record.id) + "\n")
f.write(str(seq_record.seq[421:480]) + "\n") #start 421 to end 480 base positions

fin.close()
fout.close()